The analysis of samples collected in Northwest Ohio (high strontium area) in October, 1978 will continue for as many trace elements as possible. Transfer of all analytical data to computer cards with cross reference to individual's residence and caries prevalence. Studies on the effects of strontium on tooth morphology will continue using an animal model. Further field studies will be carried out in the fall of 1979 to collect more samples for study and analysis. Emphasis will be given to the collection of plaque and studies on plaque activity, inorganic composition and microbial content.